1. Field of the Invention
The present invention relates to printers and facsimile machines, and more particularly to a printer where multiplexed print data is transferred from control circuits to corresponding one of a plurality of print heads via a common bus line.
2. Description of Related Art
An electrophotographic color printer incorporates a series of print engines of the same construction. Each print engine operates for a corresponding one of yellow, magenta, cyan, and black images. Such a system is referred to as tandem system. An LED array illuminates a photoconductive drum to form an electrostatic latent image of a corresponding color on the surface of the drum. The electrostatic latent image is then developed with a corresponding colored toner into a colored toner image. The colored toner image is then transferred to a print medium. As the print medium passes through the series of print engines, yellow, magenta, cyan, and black toner images are transferred one over the other on the print medium, thereby producing a full color image.
However, a tandem system requires a large number of interface cables which increase manufacturing cost. For example, a control circuit generates image data for each color and transfers the image data to a corresponding LED print head. Therefore, in order to communicate image data and associated control signals, a total of four sets of cables are connected between the respective LED print heads and the circuit board on which the control circuits are built.
A large number of cables necessarily increases the number of connectors and the number of pins of LSIs that connect cables, and therefore requires large circuit boards. This increases the total cost of the printer. In addition, a large number of wires radiate more noise, and therefore requires some measure for addressing increased noise radiation.
The aforementioned problems exist not only in a printer having a plurality of LED heads but in thermal transfer type printers, ink jet type printers and the like having a plurality of print heads.